Five axis riveter

ABSTRACT

Riveting apparatus for operation on a workpiece having opposite sides and supported vertically on a horizontal surface comprising a frame having a pair of spaced apart sides movable along the supporting surface and straddling the workpiece, first and second carriages movably mounted on respective sides of the frame and riveting tools on first and second heads on the first and second carriages, respectively, the tools being movable toward and away from the workpiece. The frame travels in a first direction along the supporting surface and along the workpiece, the first and second carriages are movable in a direction substantially perpendicular to the first direction and toward and away from the supporting surface, and the frame is movable in a third direction transverse to the first direction and toward and away from the workpiece. The first and second heads are movable independently about axes substantially parallel to the first direction and to the supporting surface, and both heads are movable independently about axes substantially perpendicular to the first direction and to the supporting surface. 
     The workpiece is supported by a fixture extending along the path of travel of the apparatus and the fixture is supported at spaced locations therealong above the supporting surface by retractable supports separately movable away from the fixture to provide clearance space between the fixture and the supporting surface for travel of a base of the machine. 
     In a riveting system wherein a plurality of such workpieces are supported vertically on a horizontal surface and arranged in spaced apart parallel rows, there is provided a shuttle carriage extending transverse to the workpiece paths and intersecting the paths for receiving the riveting apparatus and transferring it to any of the other workpiece paths in a manner maintaining the same orientation of the apparatus about a vertical axis during the transfer.

This application is a continuation-in-part, of application Ser. No.745,253, filed June 14, 1985, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to the art of automatic drilling and rivetingmachines, and more particularly to a new and improved automatic drillingand riveting machine for operation on major subassemblies.

One area of use of the present invention is in automatic drilling andriveting of vertically disposed workpieces, although the principles ofthe present invention can be variously applied. An example of such aworkpiece is a contoured wing panel rigidly held vertically in a fixturewherein a series of closely-spaced, horizontally disposed stringers areto be riveted to the wing panel. Because of the large size and weight ofsuch major subassemblies, it is desirable to provide an automaticdrilling and riveting machine which moves along a stationary workpiecewhile operating thereon. In the design of such a machine, an importantconsideration is providing controlled movement of the drilling andriveting tools in a significant number of directions. Another importantconsideration is providing an arrangement for supporting the verticallydisposed workpiece in a manner which does not interfere with movementand operation of the drilling and riveting machine. In addition, itwould be highly desirable to provide a simple yet effective arrangementfor transferring the machine between a series of such verticallydisposed workpieces for operation thereon.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of this invention to provide a newand improved automatic drilling and riveting machine for operation onmajor subassemblies.

It is a more particular object of this invention to provide such anautomatic drilling and riverting machine for movement along a stationaryworkpiece comprising a major subassembly while operating thereon.

It is a further object of this invention to provide such a machinehaving controlled movement of the drilling and riveting tools in asignificant number of directions.

It is a further object of this invention to provide for use with such amachine an arrangement for supporting the workpiece in a verticalposition and in a manner which does not interfere with movement andoperation of the drilling and riveting machine.

It is a further object of this invention to provide a simple yeteffective arrangement for transferring such a machine between a seriesof vertically disposed workpieces for operation thereon.

The present invention provides riveting apparatus for operation on aworkpiece having opposite sides and supported on a surface with thesides disposed substantially perpendicular to the supporting surface,the riveting apparatus comprising

a frame having a pair of spaced apart sides adapted to move along thesupporting surface and extending along the workpiece in a manner suchthat the frame sides are in straddling relation to the workpiece, firstand second carriage means movably mounted on respective sides of theframe and riveting tools on first and second head means in first andsecond positioning means on the first and second carriage means,respectively, the tools being movable toward and away from theworkpiece.

The apparatus further comprises means on the frame co-operating withmeans on the supporting surface for moving the frame in a firstdirection along the supporting surface and along the workpiece, means onthe first and second carriage means co-operating with means onrespective sides of the frame for moving the first and second carriagemeans in a direction substantially perpendicular to the first directionand toward and away from the supporting surfaces, and means for movingthe frame in a third direction transverse to the first direction andtoward and away from the workpiece.

The apparatus further comprises means on the first and second head meansco-operating with means on the first and second positioning means formoving the first and second head means independently about axessubstantially parallel to the first direction and to the supportingsurface, and means on the first and second positioning meansco-operating with means on the first and second carriage means formoving the first and second head means independently about axessubstantially perpendicular to the first direction and to the supportingsurface.

In a riveting system wherein the workpiece is supported by a fixtureextending along the path of movement of the apparatus, the fixture issupported at spaced locations therealong above the supporting surface byfixture supporting means separately movable away from the fixture toprovide clearance space between the fixture and the supporting surfacefor travel of a base of the riveting apparatus.

In a riveting system wherein a plurality of such workpieces aresupported substantially vertically on a horizontal supporting surfaceand arranged in spaced apart substantially parallel rows, there isprovided shuttle means extending transverse to the workpiece paths andintersecting the paths for receiving the riveting apparatus andtransferring it to any of the other workpiece paths in a mannermaintaining the same orientation of the apparatus about a vertical axisduring the transfer.

The foregoing and additional advantages and characterizing features ofthe present invention will become clearly apparent upon a reading of theensuing detailed description together with the included drawing wherein:

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a side elevational view illustrating the riveting apparatus ofthe present invention operating on a workpiece in the form of a majorsubassembly held in a fixture;

FIG. 2 is a plan view of the riveting apparatus and fixture of FIG. 1;

FIG. 3 is an end elevational view of the riveting apparatus and fixtureof FIG. 1;

FIG. 4 is an end elevational view of the riveting apparatus of thepresent invention;

FIG. 5 is a top plan view of the apparatus of FIG. 4;

FIG. 6 is a side elevational view of the apparatus of FIG. 4;

FIG. 7 is a view similar to FIG. 5 with parts removed and illustratingmechanisms for moving the positioning about axes perpendicular to thesupporting surface;

FIG. 8 is a side elevational view taken about on line 8--8 in FIG. 11;

FIG. 9 is a sectional view taken about on line 9--9 in FIG. 8;

FIG. 10 is a sectional view taken about on line 10--10 in FIG. 8;

FIG. 11 is a fragmentary elevational view of an arrangement including aformer board for holding the stringers in place against the wing skinduring a riveting operation of the type shown in FIG. 1;

FIG. 12 is a fragmentary elevational view of an arrangement including aformer board and strongback for holding the stringers and wing skin inthe fixture during riveting;

FIG. 13 is a plan diagrammatic view illustrating an arrangement fortransferring the riveting apparatus of the present invention betweenrows of vertically disposed workpieces for operation thereon;

FIG. 14 is an elevational view, partly in section, taken about on lines14-14 in FIG. 13;

FIG. 15 is an elevational view similar to FIG. 4 showing a portion ofthe riveting apparatus and illustrating in side elevation a transfervehicle for use in the arrangement of FIG. 13; and

FIG. 16 is a side elevational view thereof of the transfer vehicle ofFIG. 15 as it would appear in carrying the riveting apparatus.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring now to FIGS. 1-3, there is shown riveting apparatus generallydesignated 10 for operation on a workpiece, generally designated 12,having opposite sides and supported on a surface generally designated 14with the workpiece sides disposed substantially perpendicular to thesupporting surface. Typically surface 14 is the floor of a building suchas a factory. In the present illustration, workpiece 12 comprises acontoured wing panel rigidly held vertically in a fixture wherein aseries of closely-spaced, horizontally disposed stringers are to beriveted to the wing panel. In particular, as shown in FIG. 1, the wingpanel includes a wing skin designated 16 which typically comprises aseries of sections initially joined together in a suitable manner toprovide a workpiece of significant length. The stringers designated 18are in closely-spaced horizontal relation and held in place prior toriveting the wing skin by a series of vertically spaced formers 20 in amanner which will be described. The arrangement of wing skin 16,stringers 18 and formers 20 is held in a fixtures generally designated24 in a manner so as to be disposed vertically, i.e. such that theopposite sides of the workpiece are substantially perpendicular tosupporting surface 14.

The fixture 24 comprises a lower frame member or beam 26 disposedsubstantially parallel to supporting surfaces 14, an upper frame or beam28 in spaced, substantially parallel relation to frame 26, and a pair ofend frame members 30 and 32. In the arrangement shown, the opposite endsof fixture 24 are supported on surface 14 by screw jack levelingpositioners 34 to provide three leveling points on the fixture. Inaccordance with the present invention, fixture 24 also is supportedintermediate the ends thereof at spaced locations by alignment supportand correction mechanisms in the form of hydraulic screw jacks 36. Eachof the retractable supports 36 can be lowered, i.e. moved away fromfixture frame 26 toward surface 14, to provide clearance for travel ofriveting machine 10 along the workpiece in a manner which will bedescribed. A preferred form of supports includes an hydraulic cylinder37 disposed vertically in pit 38 extending below surface 14. Theworkpiece is held in fixture 24 by the master tooled header assembly 40near end 32, by the support members generally designated 44 near end 30,and by a series of V-block type clamps or holders 46 at spaced locationsbetween the lower and upper frames 26 and 28, respectively, and theadjacent edges of the workpiece 12. Header 40 is made from a master toolso that it will fit its opposite header, i.e. to insure that lefthandand righthand counterparts of bulky parts such as wing parts fittogether. A laser attitude control for horizontal/vertical alignment offixture 24 and workpiece 12 comprises a laser light source 50 on frame26 and a sensor 52 on frame 28, the light path therebetween indicated bythe broken line 54.

Machine 10 comprises a frame having spaced-apart sides and adapted tomove along workpiece 12 in a manner such that the sides of the framestraddle the workpiece 12. The machine sides are perpendicular tosupporting surface 14 and parallel to the sides of workpiece 12. One ofthe sides of machine 10 is defined by a pair of upright, spaced andparallel columns, 58 and 60 shown in FIG. 1. As shown in FIGS. 2 and 3,the opposite side of the machine frame is defined by a pair of spacedapart upright and parallel columns 62,64. The machine frame includes atop 66 disposed parallel to supporting surface 14 for joining the framesides, in particular, the columns 58,60,62 and 64 at the upper endsthereof as viewed in FIGS. 1-3. The machine frame also includes a baseor bottom 68 disposed parallel to and located near supporting surface 14and supporting the columns 58, 60, 62 and 64 at the lower ends thereof.

The riveting machine frame is adapted to move along track means onsupporting surface 14 and extending along workpiece 12. In thearrangement shown, there is a pair of spaced apart, parallel track rails70,72 each extending along a corresponding side of the arrangement ofworkpiece 12 and fixture 24. Movement of machine 10 is guided alongrails 70,72 by means of wheels, for example, two of which wheelsdesignated 74,76 in FIG. 1, which are rotatably connected in a suitablemanner to base 68 and engage the rails 70, 72. One wheel can be sprunghydraulically so that all four wheels carry an equal load even thoughthe tracks may be slightly misaligned in elevation, i.e. in the vericaldirection as viewed in FIGS. 1 and 3. A third rail 80 shown in FIG. 3extends outwardly of, close to and parallel to one of the rails, forexample rail 72 and serves as a drive rail and power bus. Machine 10 canbe driven along rails 70,72 by means of a driven pinion on machine 10engaging a rack on a rail in a manner which will be described in moredetail presently. Alternatively, the wheels may be driven.

The riveting machine 10 of the present invention further comprises firstand second carriage means 84 and 86, respectively, movably mounted onrespective sides of the machine frame. Carrages 84,86 are movable towardand away from supporting surface 14 in directions parallel to the sidesof the machine frame in a manner which will be described. This directionis substantially perpendicular to the above-described direction ofmovement of machine 10 along the tracks. The carriages 84 and 86, inturn, support and carry first and second positioners 88 and 89,respectively, which in turn support and carry first and second blockmeans or head means 90 and 92, respectively. The heads 90,92 in turn,carry drilling and riveting tools for operation on workpiece 12 and aremovable relative to the respective carriages 84,86 and positioners 88,89in a manner which will be described.

The machine 10 also is provided with platforms 96 and 98 which extendout from the opposite sides for carrying other components of themachine. For example, in the machine shown, platform 96 carries an aircompressor 100, refrigerator-dryer 102 for treatment of the air and anhydraulic pump and fluid cooler 104. Platform 98 carries a hopper 106for storing rivets and cabinet 108,110 for housing various controls.

FIGS. 4-6 are enlarged views of the riveting machine 10 of FIGS. 1-3.The heads or blocks 90,92 carry riveting tools and relatedinstrumentalities. A rivet bucking tool 116 is mounted on a fixed axiswith respect to upset head 90 and is adapted to be reciprocated by anhydraulic cylinder 118. This axis is the central operating axis, i.e.the drilling and riveting axis of machine 10. Movement of bucking tool116 is toward and away from the workpiece, i.e. along a path extendingin a direction through the sides of the workpiece. The drill/buck/shaveor head 92 carries, drilling, riveting and shaving tool assemblies. Forexample the tools can be carried on a transfer plate (not shown) adaptedto be moved in a direction normal to the above-identified operationalaxis to selectively place the tools in alignment with that axis. In theillustration of FIG. 4, the tool shown is a shaving tool 120 forsmoothing the rivet heads after upset. For a more detailed descriptionof an arrangement of linearly spaced drilling and riveting tools on areciprocating transfer plate, reference may be made to U.S. Pat. No.3,534,896 issued Oct. 20, 1970 entitled "Riveting Machine" and assignedto the assignee of the present invention, the disclosure of which ishereby incorporated by reference.

The tools carried by the transfer plate are moved by suitable means,such as by hydraulic cylinders, toward and away from the workpiece alongpaths which extend in a direction through the sides of the workpiece. Apressure foot bushing 124 also is carried by block 92 by means of spacedapart pneumatic cylinders 126,128. The bushing 124 is adapted to contactthe workpiece around the location to be drilled and riveted, and thedrilling and riveting tools move through a central opening in thebushing for contacting the workpiece. For a more detailed description ofa pressure foot bushing and operation in drilling and rivetingapparatus, reference may be made to U.S. Pat. No. 3,557,442 issued Jan.26, 1971 entitled "Slug Riveting Method And Apparatus" and assigned tothe assignee of the present invention, the disclosure of which is herebyincorporated by reference.

Movement of riveting machine 10 along tracks or rails 70,72 and 80 andhence along workpiece 12 in fixture 24 is provided in the presentillustration by a rack and pinion drive. A gear box 130 carried by base68 of the machine frame is driven by a servo motor 132. A pinion 134 onthe output of gear box 130 meshes with a rack 136 on one of the rails,for example rail 72. For a more detailed description of a rack andpinion drive for a large riveting machine along a track, reference maybe made to the aforementioned U.S. Pat. No. 3,534,896. The movement ofmachine 10 along the rails and along workpiece 12 is in a direction alsodesignated the X axis. The exact location of machine 10 along the X axisis known at all times as derived from encoder feedback to the machinecontrol. Alternatively, the wheels can be driven directly with periodicverification of position.

Carriages 84, 86 are movable in opposite directions along pathsperpendicular to the supporting surface 14. These paths areperpendicular to the X axis and are identified also as the Y axis. Thereis provided means on the carriage means 84,86 cooperating with means onthe respective sides of the machine frame for moving carriages 84,86 inthe foregoing manner. In particular, a pair of ball screws 140 and 142are provided, one on each side of the machine frame and rotatablyconnected at opposite ends, for example, in brackets 144 and 146,respectively, fixed to frame top 66 and suitable means (not shown)adjacent frame bottom 68. Nut members 148 and 150 are threaded on screws144 and 146, respectively, and engage extensions 152 and 154,respectively, on carriages 84 and 86, respectively. Each ball screw andnut assembly is driven by a right angle gear box powered by single servomotor, for example the drive indicated 158 in FIG. 6. The ball screw andnut assembly are matched and preloaded, and the carriages 84,86 aresynchronously indexed along the Y axis, with encoder feedback to themachine control for monitoring the location. The arrangement alsoincludes suitable means for counterbalancingthe weight. Movement ofcarriages 84,86 is guided by engagement between rollers 159 on carriages84,86 which ride along tracks 160 on the frame columns.

Machine 10 further comprises means for moving the frame in a transversedirection with respect to the workpiece to move the frame sides towardand away from the workpiece. The frame sides are movable in unison inthis direction, which also is transverse to the direction of the rails70,72 and which is designated the Z axis. The combination of columns 58,60, 62 and 64 fixed to and depending from top 66 comprises a tied columnstructure. This structure is movably supported on the frame base orbottom 68 in the following manner. Columns 58, 60, 62 and 64 areprovided with wheels 162, 164, 166 and 168, respectively, rotatablyconnected to the lower ends of the corresponding columns and contactingsupporting surfaces on platforms in the form of slides 170, 172, 174 and176, respectively, in frame base 68. The wheel axles are oriented toallow the above-identified transverse movement of the tied columnstructure. The structure is moved or indexed by a ball screw and nutassembly driven by a servo generally designated 180 in FIG. 4 whereinthe ball screw is rotatably connected in frame base 68 and the nutmember engages a surface of the tied column struhcture in a mannersimilar to that of the Y axis carriage drive. In the apparatus shown,the nut member of Z axis drive 180 operatively engages the lower end ofcolumn 64. Similar Z axis drive arrangements can be provided adjacent tothe lower ends of the other three columns.

Machine 10 further comprises means on the first and second head means 90and 92, respectively, co-operating with means on the first and secondpositioners 88 and 89, respectively, for moving the first and secondhead means 90,92 independently about axes substantially parallel tosupporting surface 14 and the X axis. This direction is also designatedthe a axis and is normal to the plane of the paper as viewed in FIG. 4.Thus, each of heads 90,92 is pivotal about an axis, i.e. the a axis,generally parallel to the X axis. Movement of heads 90,92 is provided byrack and pinion drive arrangements in the heads and correspondingpositioners. For example, as shown in FIG. 4, an arcuate rack 184 onhead 90 is in meshing engagement with a pinion 186 rotatably mounted onpositioner 88 and driven by a motorized gearbox 188 on positioner 88.Movement of head 90,92 about the a axis in positioners 88,89 is guidedby co-operative engagement between bearings 190 and arcuate tracks 192on both of the respective components. Only the arrangement on head 90 isshown in FIG. 4 for convenience. The gearboxes for both head preferablyare driven by servo motors which drive the gear segments withinestablished travel limitations determined by appropriate sensors, andthe a axis travel of each head 90,92 can be matched through axiscalibration at the machine control.

Machine 10 further comprises means on the first and second positioners88 and 89, respectively, co-operating with means on the first and secondcarriage means 84 and 86, respectively, for moving the first and secondpositioners and with them the first and second head means independentlyabout axes substantially perpendicular to supporting surface 14 andsubstantially parallel to the Y axis. This direction is also designatedthe b axis and is normal to the plane of the paper as viewed in FIG. 5.Thus, each of the positioners 88 and 89 and corresponding one of theheads 90,92 is pivotal about an axis, i.e. the b axis, generallyparallel to the Y axis. The positioners 88 and 89, and therefore theheads 90 and 92, are supported by trunnions mounted within the carriage84 and 86, respectively, and each positioner 88,89 is driven within theb axis travel limits by a d.c. servo motor and ballscrew and nutassembly. In particular, as shown in FIGS. 7 and 8, a servo motor 200 isheld by a trunnion bracket 202 connected to a b axis support beam 203fixed to carriage 86. A ball screw assembly 204 driven by motor 200 isoperatively associated with a trunnion assembly 206 connected by abracket 208 to positioner 89. An identical arrangement of servo motor200', trunnion bracket 202' , b axis support beam 203 ballscrew assembly204', trunnion assembly 206', and bracket 208' is provided forpositioner 88 and carriage 84. For convenience, only the arrangement forpositioner 89 and carriage 86 will be described in further detail, itbeing understood that the arrangement for positioner 88 and carriage 84is identical in structure and operation.

FIGS. 9 and 10 are enlarged views showing in further detail theoperative relationship between ball screw assembly 204 and trunnionassembly 206. A nut member 210 on screw 204 has one end within trunnionassembly 206 and is housed within a ball nut guard 212. The end of screw204 opposite motor 200 is supported within an arrangement of radialbearing 214 and bearing housing 216 which can be supported on carriage86. Trunnion assembly 206 includes a trunnion plate 220 to which the endof nut 210 is fixed and through which screw 204 rotatably extends and apair of diametrically opposed trunnion pins 222 and pin bushings 224 formounting t5trunnion plate 220 within a trunnion ring 226. Another pairof diametrically opposed trunnion pins 228 and pin bushings 230, spacedninety degrees from the other pins and bushings, connect trunnion ring226 to bracket 208. Rotation of screw 204 in either direction moves nut210 to the left or right in FIG. 10 to pivot trunnion 206 and bracket topivot positioner 89 and with it head 92 about the b axis.

Movement of heads 90,92 about the b axis in carriages 84,86 is guided byco-operative engagement between bearings 234 and arcuate tracks 236 onthe respective components. Movement of head 90,92 about the b axis canbe under closed loop sensor control and the travel of each positioners88,89 and with them head can be matched through axis calibration at themachine control.

FIG. 11 illustrates in further detail one of the formers 20 in thearrangement of FIG. 1. It comprises an elongated board 240 having oneside 242 curved to on conform to the surface of the workpiece, i.e. wingskins 16, and provided with a series of spaced notches or recesses 244to receive stringers 18. The opposite side of board 240 can be straight.A clamp 246 secures skin 16 to board 240 at the upper end of thearrangement of FIG. 11 and a V-block member 248 further supports wingskin 16 at the lower end.

FIG. 12 illustrates an alternative arrangement for use in some rivetingapplications wherein the combination of former board 240, wing skin 16and stringers 18 is fastened to a strongback 254 which, in turn, istightly held between upper and lower frames 28' and 26', respectively ofa fixture. Strongback 254 is in the form of an elongated board having acurved side 256 confirming to the curvature of skin 16 and having astraight opposite side. Former board 240 is connected to strongback 254by suitable fasteners 258. The overall width of the arrangement of FIG.12 is greater than that of FIG. 11 and is considered in providing themovement capability of machine 10 in the Z axis direction.

Riveting machine 10 of the present invention operaes in the followingmanner. The machine 10 travels along workpiece 12 and fixture 24 in theX axis direction as shown in FIG. 1 to move successively to variouslocations on workpiece 12 to be drilled and riveted. During movement ofmachine 10 in this direction, the individual retractable supportingcylinders 36 move downward, one-by-one, to surface 14 or below if arecess is provided to allow riveter 10 to move to the next location. Asthe machine 10 passes, the particilar cylinder 36 rises to support theworkpiece once again. In conjunction with movement of machine 10 alongthe X axis, carriages 84,86 are movable along he Y axis to reachadditional locations to be drilled and riveted. In addition, movement ofheads 90 and 92 about the a and b axes accommodate the surface contourof the workpiece 12. At each location of fastening, machine 10 goesthrough the typical sequence of drilling the workpiece, rivet insertionand upset, and rivet head shaving. Pressure foot bushing 124 and buckingram 116 contact opposite sides of the workpiece 12 and each of the toolsis movale into alignment with the drilling and riveting axis, toward andaway from the workpiece and out of alignment with the axis. Theforegoing operations are well known to those skilled in the art, and fora more detailed description thereof, reference may be made to theabove-referenced patents 3,534,896 and 3,557,442.

By way of example, where workpiece 12 comprises the vertical wing skin16 and horizontal stringers 18 shown in FIG. 1, the axis motions ofmachine 10 are as follows: X is travel along the wing span, Y is travelalong the chord length, Z is travel to compensate for chord height, a isrotation about the X axis and b is rotation about the Y axis. The X, Y,Z, a and b motions allow machine 10 to align the riveting process normalto any point on the workpiece within an established work envelope. The Xand Y axes can be programmable and addressable axes. The Z, a and bmotions can be controlled by a closed loop normality sensor servo systemwhich traces the aerodynamic surface of the workpiece.

For tool-to-tool alignment, along the drilling and riveting axis, heads90,92 can be mechanically geared together vertically through matchedball screws, matched right angle gear boxes and a single drivemotor-gear-reducer-hydraulic counterbalance arrangement. A axis anglecontrol can be through a simultaneous signal feed to two servo drives,each having an axis calibration supplied by the machine control so thatslight deviation from the true position can be corrected. B axis anglecontrol likewise can be through a second set of servo drives, againprovided with axis calibration. The a and b axis originate at the workouter surface. The origins are held to that point by a Z axis movementsensor and associated servo motor and feedback loop. This is so that aminor deviation in the a or b attitude will have no effect on the X or Yposition.

Machine 10 can move along workpiece 12 in fixture 24 several ways toaccommodate the presence of formers 20. For example, machine 10 can movein the X direction for riveting up to a former, then in the Z directionaround the former and then in the X direction for continued riveting upto the next former and so as along the workpiece 12. The machine 10 canreturn to allow riveting in its location as machine 10 proceeds in thereturn direction. After machine 10 rivets and proceeds away from thelocation of a removed former it is replaced. The removal and replacementof formers 20 can be done manually or automatically by machine, eitherunder control of riveter 10 or in response to a central control.Alternatively, machine 10 can move in a forward X direction for rivetingup to a former, move in the reverse X direction a small distance toallow removal of the former either manually or by machine, then proceedin the forward X direction to rivet in the location of the former andbeyond whereupon the former is returned to its position.

FIGS. 13 and 14 are diagrammatic views of a riveting system according tothe present invention including a plurality of riveters identical toriveter 10 and a plurality of workpieces and fixtures similar toworkpiece 12 and fixture 24. In the system shown, there are eightworkpieces 12a-12h supported in eight fixtures 24a-24h. The workpieceand supporting fixtures are arranged in four spaced-apart, mutuallyparallel rows comprising a first set, and another, four spaced-apart,mutually parallel rows in longitudinal alignment with the first fourrows and comprising a second set. The workpiece and correspondingfixtures are disposed perpendicular to, i.e. vertically, a supportingsurface 14'. In the system shown there are four riveters 10a, 10b, 10cand 10d each of the type like riveter 10 of FIGS. 1-10 including a framehaving a pair of spaced apart sides adapted to move along track means onthe supporting surface extending along a workpiece in a manner such thatthe frame sides are in straddling relation to the workpiece and carrydrilling and riveting tools that are movable toward and away from theworkpiece. In the present illustration of riveting stringers to wingskins, the eight workpieces 12a-12h can comprise the left wing rearlower skin, left wing rear upper skin, left wing front lower skin, leftwing front upper skin, right wing rear lower skin, right wing rear upperskin, right wing front lower skin, and right wing front upper skin,respectively. The travel path for each riveter along each workpiece andfixture is defined by spaced-apart, parallel tracks 70a, 72a-70h, 72h.In addition, the tracks of aligned rows are also aligned i.e. tracks70a,72a are in longitudinal alignment with tracks 70e,72e and so onthrough the entire arrangement. Along each row there is an X axis drivepower bars and track 270a-270h, and tracks of aligned or opposite rowsare aligned, for example tracks 270a and 270e.

In the illustrative arrangement shown riveters 10a-10d are located onthe paths containing workpieces 12a-12d, respectively. The system of thepresent invention enables any riveter to be moved to any workpiece andfixture area in the arrangement of FIGS. 13 and 14 or to an out ofservice location for maintenance. To this end there is provided shuttlecarriage means adapted to receive and carry any riveter and movablealong means defining a shuttle path extending in a direction transverseto and in communication with, i.e. intersecting, the workpiece paths. Asthe riveter is received and carried by the shuttle carriage itsorientation about the Y axis is not changed, and when the destination isreached the riveter simply can move off the carriage without changingposition and is immediately ready for travel along the row where it isleft by the shuttle carriage.

As shown in FIG. 14, the shuttle carriage means comprises a carriage 274of welded steel construction which travels within a shallow pit 276extending tranverse to track 70a,72a-72h, to any of the four interfacelocations shown in FIG. 13. For convenience, these four interfacelocation are indicated by the representation of shuttle carriage 274 andriveter 10 shown in broken lines. Carriage 274 is supported by wheeltrack assemblies 280 of sufficient size to support the weight of theriveter and be electrically driven. To this end, rails 282,284 extendalong the bottom of pit 276. The top 286 of shuttle carriage 274 issubstantially flush with supporting surface 14 and is provided withtrack assemnblies 290,292 and a power trolley matching those utilized tofacilitate riveter X axis travel. The tracks 290,292 are aligned withthe tracks 70,72 at each intersection point allowing the riveter X axisdrive to power directly onto the shuttle carriage 274. The carriage 274has its own controller and operator. As shown in FIG. 13, pit 276extends beyond the rows containing workpiece 12d, 12h to an out ofservice shunt location 296 for maintenance or storage. If desired, shuntside tracks at location 296 can be provided, extending perpendicular topit 276, for temporary removal of a riveter from th shuttle carraige.

Thus, one riveter can be taken out of service by moving it to the shuntsection 296, and by replacement of a fixture in place with a workpiece,the appropriate riveter can be brought out of the shunt section andmoved on line using the shuttle carriage 274 to move the riveter to theassembly area where used. Although the shuttle or traverse carriage 274is used primarily to move riveters to and from assembly areas and to andfrom out of service or maintenance areas, when empty the shuttlecarriage 274 can serve as a bridge over the shuttle or traverse pit 276.

FIGS. 15 and 16 are enlarged views showing in further detail the shuttleor traverse carriage 274 and pit 276. As shown in FIG. 15, on the topsurface 286 of carriage 274 is provided with a pair of spaced apartrails 290,292 onto which a riveter 10 is moved and supported forconveyance by carriage 274 along the transverse path defined by pit 276.As shown in FIG. 16, shuttle carriage is driven by a rack and pinionarrangement including a rack 300 on one of the tracks in pit 276, forexample track 284, which is engaged by a pinion 302 driven by amotorized gear box 304 on carriage 274. Electric power is supplied by arail 308. Alternatively, the shuttle carriage wheels can be drivendirectly.

As previously mentioned, one of the four wheels providing movement offastening machine 10 in the X direction is sprung by flexible supportingmeans, preferably fluid operated, so that the wheel carries its share ofthe load independent of vertical position over a short travel. Foraccurate placement of fasteners, it is of utmost importance that the twotracks along which machine 10 travels be parallel in both plan andelevation. As shown in FIG. 15, one of the wheels, for example wheel 76,is hydraulically sprung so that all four wheels of machine 10 carry anequal load even though the tracks 70,72 may be slightly misaligned inelevation. Such vertical misalignment can occur over the large extent ofsurface 14 travelling along the length of the workpiece 12. As shown inFIG. 15, the wheel bearing assembly and axle 310 are carried by blockmeans 312 having a pair of arm-like side members joined by a web toprovide a fork-like structure which rides up and down between gibs 314which are fixed to be stationary with respect to the machine frame. Theflexible supporting means is in the form of an hydraulic cylinder 316the housing of which is fixed to the machine frame and the piston rod ofwhich is connected to block means 312. Cylinder 316 is provided withcontrolled pressure to provide a maximum stroke in the verticaldirection of about one-quarter inch.

It is a therefore apparent that the present invention accomplishes itsintended objects. While embodiments of the present invention have beendescribed in detail, that is for the purpose of illustration, notlimitation.

We claim:
 1. Riveting apparatus for operation on a workpiece havingopposite sides and supported on a surface with said sides disposedsubstantially perpendicular to said supporting surface, said rivetingapparatus comprising:(a) a frame having a pair of spaced apart sidesadapted to move along said supporting surface and extending along saidworkpiece in a manner such that said frame sides are in straddlingrelation to said workpiece; (b) first and second carriage means movablymounted on respective sides of said frame; (c) first and secondpositioning means carried by said first and second carriage means,respectively; (d) riveting tools on first and second head means on saidfirst and second positioning means, respectively, said tools beingmovable toward and away from said workpiece; (e) means on said frameco-operating with means on said supporting surface for moving said framein a first direction along said supporting surface and along saidworkpiece; (f) means on said first and second carriage meansco-operating with means on respective sides of said frame for movingsaid first and second carriage means in a direction substantiallyperpendicular to said first direction and toward and away from saidsupporting surface; (g) means for moving said frame in a third directiontransverse to said first direction and toward and away from saidworkpiece; (h) means on said first and second head means co-operatingwith means on said first and second positioning means for moving saidfirst and second head means independently about axes substantiallyparallel to said first direction and to said supporting surface; and (i)means on said first and second positioning means co-operating with meanson said first and second carriage means for moving said first and secondpositioning means and with them said first and second head meansindependently about axes substantially perpendicular to said firstdirection and to said supporting surface.
 2. Apparatus according toclaim 1, wherein said means on said supporting surface comprises trackmeans and said means for moving said frame in said first directioncomprises drive means co-operating between said track means and saidframe.
 3. Apparatus according to claim 1, wherein said means for movingsaid first and second carriage means comprises a driven ball screw andnut assembly for each of said carriage means.
 4. Apparatus according toclaim 1, wherein said frame comprises at least one column on each ofsaid sides and said columns are joined at the top thereof to provide atied column structure, and wherein said frame further comprises a baseand said columns are supported at the lower ends thereof on said base ina manner allowing movement of said tied column structure in said thirddirection.
 5. Apparatus according to claim 4, wherein said means formoving said frame in said third direction comprises drive means carriedby said base and operatively connected to at least one of said columns.6. Apparatus according to claim 1, wherein said means for moving saidfirst and second head means about axes substantially parallel to saidfirst direction comprises co-operating arcuate rack and pinion drivemeans on each of said first and second head means and said first andsecond positioning means.
 7. Apparatus according to claim 1, whereinsaid means for moving said first and second positioning means about axessubstantially perpendicular to said first direction comprises a trunnionassembly connected to each of said positioning means and a ball screwand nut assembly operatively associated with said trunnion assembly anddriven by motor means carried by the corresponding one of saidcarriages.